My jeep is getting stuck in four wheel drive. After it sits for about thirty minutes with the lever in two wheel drive position then it will actually go in to two wheel drive. The lever moves freely it just does not cause it to disengage the four wheel drive. Any thoughts on this? Could it be a vacuum issue?

Well from experience I know that the best thing to do for the cases sake is to back up if you take it out of 4wd, I always do it or I dont take it out tell I can back up, just a few feet and you will hear or feel it pop out of 4wd

Even if the vac. disco isn't working properly the TC is what activates/disengages the front driveshaft. Make sure the lever is all the way down and try backing up. If that dosn't do it, check the linkage on your TC.